ADVANCED BURNING STAGES AND FATE OF 8-10M☉STARS

Jones, S.; Hirschi, R.; Nomoto, K.; Fischer, T.; Timmes, F. X.; Herwig, F.; Paxton, B.; Toki, H.; Suzuki, T.; Martínez-Pinedo, G.; Lam, Y. H.; Bertolli, M. G.

Abstract

The reaction of either 4,4′,6,6′-tetramethyl-2,2′-bipyridine, L, or 4,4′,6,6′-tetracarboxy-2,2′-bipyridine, H4L, with Cu(OAc)2·H2O under acidic hydrothermal conditions (50:1 H2O/HNO3; 160 °C) led to the formation of crystalline {[Cu(HL′)(H2O)]·H2O}, 1, which was structurally characterised to identify H3L′ as 4,4′,6-tricarboxy-2,2′-bipyridine. Clearly, in situ mono-decarboxylation of a tetracarboxylic acid ligand gave the tricarboxy-analogue, H3L′. The structure of 1 consists of a 1D coordination polymer that cross-links through hydrogen-bonding between adjacent carboxylic acid and carboxylate groups, as well as through an aqua ligand and lattice water molecule, to form a densely interconnected 3D network. Regioselective mono-decarboxylation of L or H4L at the 6′-carboxylic acid position may also be affected by heating L or H4L in acidic solution under hydrothermal conditions (2:1 H2O/HNO3; 160 °C) to yield crystalline 4,4′,6-tricarboxy-2,2′-bipyridinium nitrate hydrate {[H4L′][NO3]·H2O}, 2, which was also structural characterised. The structure of 2 features an array of hydrogen-bonding interactions that generate a 3D network. More forceful heating of the acidic solution at 180 °C led to double decarboxylation and the formation of 4,4′-dicarboxy-2,2′-bipyridine, whereas heating at 200 °C led to total decarboxylation and the formation of 2,2′-bipyridine. Details of the structures of 1 and 2 along with their synthesis are discussed.

Citation

Jones, S., Hirschi, R., Nomoto, K., Fischer, T., Timmes, F. X., Herwig, F., …Bertolli, M. G. (in press). ADVANCED BURNING STAGES AND FATE OF 8-10M☉STARS. Astrophysical Journal, 772(2), 150. https://doi.org/10.1088/0004-637x/772/2/150

• Journal Article Type: Article
• Acceptance Date: Jun 4, 2013
• Online Publication Date: Jul 17, 2013
• Deposit Date: Jun 14, 2023
• Journal: The Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 772
• Issue: 2
• Pages: 150
• DOI: https://doi.org/10.1088/0004-637x/772/2/150
• Keywords: nuclear reactions, nucleosynthesis, abundances; stars: AGB and post-AGB; stars: evolution; stars: neutron; supernovae: general